Library apparatus having accessor with bar code reader which rotates at a different horizontal position when reading a bar code failed at a first position

ABSTRACT

A library apparatus having an accessor equipped with a bar code reader. The library apparatus includes a recording medium drive unit for writing and reading data to and from a recording medium cartridge; a cartridge entry unit for entering recording medium cartridges into the apparatus; and an automatic cartridge exit unit for automatically ejecting recording medium cartridges from inside the apparatus. The accessor transports cartridges through the cell unit, the recording medium drive unit, the cartridge entry unit and the automatic cartridge exit unit. The library apparatus also includes a door for allowing a large number of recording medium cartridges to enter all at once into the cells of a given cell column of the cell unit. Because the accessor is equipped with the bar code reader, the bar code of each cartridge is read thereby every time a cartridge is taken out of its cell by the accessor.

RELATED APPLICATION

This is a continuation of application Ser. No. 08/063,275, filed on May18, 1993, now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a recording medium library apparatusand, more particularly, to a magnetic tape library apparatus having anaccessor equipped with a bar code reader.

2. Description of the Related Art

Magnetic tape-units are one of diverse kinds of external storage devicesfor use with computers. The magnetic tape units operate most commonly onwhat is known as the open reel system using 0.5-inch wide tapes. Thechores of manually loading the open reels have been alleviated bywidening acceptance of automatic tape loading devices. With thesedevices, the operator need only set a desired tape reel onto a receptorwhich then causes the tape to be loaded automatically. Today, operators'burdens are further alleviated by the widespread use of magnetic tapecartridges. A magnetic tape cartridge, accommodating a tape having thesame width as that of open reel tapes, allows the tape to be threadedout of the reel within for automatic tape loading.

A plurality of magnetic tape cartridges are entered in the magnetic tapelibrary apparatus. Any one of the cartridges is selected and loaded to amagnetic tape drive unit for data recording and reproduction. Themagnetic tape library apparatus comprises a cell unit having a pluralityof cells each accommodating a magnetic tape cartridge; a magnetic tapedrive unit for recording and reproducing data; and an accessor forautomatically switching magnetic tape cartridges between cell unit andmagnetic tape drive unit. The magnetic tape library apparatus furthercomprises a cartridge entry unit for entering magnetic cartridges intothe library apparatus, and an automatic cartridge ejection unit forautomatically ejecting magnetic tape cartridges from inside the libraryapparatus.

The accessor transports magnetic tape cartridges through the magnetictape drive unit, cell unit, cartridge entry unit and automatic cartridgeejection unit. Magnetic tape library apparatuses of this kind are widelyused as an external mass storage device for computers. These apparatusesare required to operate unfailingly when unattended.

The cartridge entry unit transports one by one a plurality of cartridgesentered by the operator. The accessor receives each cartridge and storesit into the appropriate cell of the cell unit. More specifically, thecartridge entry unit has a bar code reader that reads a bar code offeach of the cartridges entered. The bar code data thus read are sent toa host computer via an accessor controller. In turn, the host computerspecifies the address of the cell into which the accessor places theapplicable cartridge. For writing and reading of data to and from amagnetic tape cartridge, the host computer first designates the addressof the cell from which the accessor extracts the cartridge. Theextracted cartridge is loaded into the magnetic tape drive unit. Afterdata are written to and/or read from the magnetic tape cartridge, theaccessor takes out the cartridge from the magnetic tape drive unit andbrings it into the cell whose address is again specified by the hostcomputer.

With prior art magnetic tape library apparatuses, a plurality ofcartridges in the cartridge entry unit are separated one by one fordelivery to the accessor. The accessor brings each separated cartridgeinto the appropriate cell. The procedure takes time if there are a largenumber of cartridges to be accommodated into the cell unit. One proposedsolution to this drawback is to provide an opening on the housing closeto the cell unit, the opening allowing a large number of cartridges tobe entered all at once into the cell unit. One disadvantage of thissolution is as follows: because the bar code reader is provided in thecartridge entry unit, each of the numerous cartridges entered into thecells of the cell unit must be extracted one by one by the accessor andbrought to the bar code reader that reads a bar code off each cartridge.With its bar code read, each cartridge must be stored again into theapplicable cell. In this case, too, it takes time to read the bar codeoff each of the numerous cartridges entered and to direct them to thecells having the appropriate addresses.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a libraryapparatus capable of quickly reading bar codes off a large number ofcartridges entered directly and all at once into a cell unit, wherebythe time required for addressing the cartridges in the cell unit isshortened.

In accordance with an aspect of the present invention, there is provideda library apparatus comprising: a housing; a cell unit having aplurality of cell columns each including a plurality of cells, each cellaccommodating a recording medium cartridge having a bar code attachedthereto; a recording medium drive unit for writing and reading data toand from a recording medium cartridge; a cartridge entry unit forentering recording medium cartridges into the library apparatus; anautomatic cartridge exit unit for automatically ejecting recordingmedium cartridges from inside the library apparatus; an accessor fortransporting cartridges through the cell unit, the recording mediumdrive unit, the cartridge entry unit and the automatic cartridge exitunit, the accessor including a hand mechanism for gripping a cartridgein a substantially horizontal manner; and a bar code reader attached tothe hand mechanism for reading the bar code off each recording mediumcartridge.

In a preferred structure according to the invention, the libraryapparatus further comprises a door for allowing a large number ofrecording medium cartridges to enter all at once into the cells of agiven cell column of the cell unit. The door is attached pivotably tothe housing adjacent to the cell unit. The hand mechanism of theaccessor comprises a base attached swingingly about a vertical axis, andgrip means for gripping the recording medium cartridge disposed movablyon the base between an advanced position and retracted position. The barcode reader reads a bar code off the recording medium cartridge afterthe grip means gripping the cartridge has moved to the retractedposition.

In accordance with another aspect of the present invention, there isprovided a library apparatus comprising: a housing; a cell unit having aplurality of cell columns each including a plurality of cells, each cellaccommodating a recording medium cartridge having a bar code attachedthereto; a recording medium drive unit for writing and reading data toand from a recording medium cartridge; a cartridge entry unit forentering recording medium cartridges into the library apparatus; anautomatic cartridge exit unit for automatically ejecting recordingmedium cartridges from inside the library apparatus; an accessor fortransporting cartridges through the cell unit, the recording mediumdrive unit, the cartridge entry unit and the automatic cartridge exitunit, the accessor including a hand mechanism for gripping a cartridgein a substantially horizontal manner; a bar code reader attached to thehand mechanism for reading the bar code off each recording mediumcartridge; and accessor control means for controlling the accessor, theaccessor control means including baud rate varying means; the bar codereader comprising a nonvolatile memory for storing baud rates, writecontrol means for writing to the nonvolatile memory a desired baud raterelevant to the communication with the accessor control means inaccordance with commands therefrom, and baud rate setting means forsetting for the bar code reader the desired baud rate written in thenonvolatile memory.

The above and other objects, features and advantages of the presentinvention and the manner of realizing them will become more apparent,and the invention itself will best be understood from a study of thefollowing description and appended claims with reference to the attacheddrawings showing some preferred embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front perspective view of a magnetic tape library apparatusembodying the invention;

FIG. 2 is a rear perspective view of the embodiment of FIG. 1;

FIG. 3 is a perspective view showing how a magnetic tape cartridge isentered into the library apparatus through a cartridge entry opening;

FIG. 4 is a perspective view depicting how a magnetic tape cartridge isentered directly into a cell of a cell drum;

FIG. 5 is a schematic plan view of the library apparatus with a topplate of its housing removed;

FIG. 6 is a schematic perspective view showing the inside of the libraryapparatus;

FIG. 7 is a schematic perspective view of an accessor drive mechanism;

FIG. 8A is an external perspective view of a magnetic tape cartridge;

FIG. 8B is a bottom view of the magnetic tape cartridge;

FIG. 9 is a front view of a magnetic tape cartridge entry unit;

FIG. 10 is a view showing the path through which a cartridge istransported by the magnetic tape cartridge entry unit;

FIGS. 11A and 11B illustrate how a gate sensor mechanism of theembodiment works, FIG. 11A showing a cartridge being erroneouslyentered, FIG. 11B depicting a cartridge being normally entered;

FIGS. 12A through 12C are plan views of the gate sensor mechanism, FIG.12A showing a cartridge being entered inversely, FIG. 12B depicting acartridge being incompletely entered, FIG. 12C portraying a cartridgebeing normally entered;

FIG. 13 is a schematic plan view of a hook mechanism;

FIGS. 14A and 14B are schematic front views of the hook mechanism in thecartridge entry unit, FIG. 14A showing the hooks being opened, FIG. 14Bdepicting the hooks being closed;

FIGS. 15A and 15B are schematic front views of the stage and hookmechanisms in the cartridge entry unit, FIG. 15A showing the stage atits highest position, FIG. 15B depicting the stage at its lowestposition with the lowest-positioned cartridge being separated from theother cartridges;

FIGS. 16A and 16B are schematic side views of a feeder mechanism in thecartridge entry unit FIG. A showing the feeder being opened, FIG. 16Bdepicting the feeder being closed;

FIGS. 17A and 17B are schematic side views of a shutter mechanism in thecartridge entry unit, FIG. 17A showing the shutter being opened, FIG.17B portraying the shutter being closed;

FIG. 18 is a front view of an automatic cartridge exit unit;

FIG. 19 is a side view of a cartridge transport mechanism in theautomatic cartridge exit unit as it grips a cartridge;

FIG. 20 is a side view of the cartridge transport mechanism as itreleases a cartridge;

FIG. 21 is a longitudinal sectional view of a tray assembly in theautomatic cartridge exit unit;

FIG. 22 is a partially broken front view of a tray driving mechanism inconnection with the tray assembly;

FIG. 23 is a partially broken longitudinal sectional view of the traydriving mechanism in connection with the tray assembly;

FIG. 24 is a perspective view of a hand mechanism;

FIG. 25 is a plan view of a grip hand and a mechanism for driving thesame;

FIGS. 26A through 29A and 26B through 29B are plan and side views,respectively, showing how the hand mechanism inserts a cartridge intothe magnetic tape drive unit;

FIGS. 30A through 33A and 30B through 33B are plan and side views,respectively, depicting how the hand mechanism inserts a cartridge intoa cell of the cell drum;

FIGS. 34A and 34B are partial sectional side views illustrating how thehand mechanism extracts a cartridge from inside a cell of the cell drum;

FIG. 35 is a schematic perspective view of a cell drum drivingmechanism;

FIG. 36 is a view outlining how the cell drum is controlled in rotation;

FIG. 37A is a view showing how a cartridge is accommodated normally in acell;

FIG. 37B is a view depicting how a cartridge is accommodated erroneouslyin a cell;

FIG. 38 is a schematic perspective view illustrating part of a faultycartridge entry detecting mechanism;.

FIG. 39 is a schematic plan view of the faulty cartridge entry detectingmechanism with its rocking arm omitted;

FIG. 40 is a partial sectional front view of the faulty cartridge entrydetecting mechanism;

FIG. 41 is a schematic plan view of the faulty cartridge entry detectingmechanism with its actuator omitted, the figure highlighting how a latchattached to the rocking arm and a lock pin are engaged with each other;

FIG. 42A is a schematic view showing the relationship between a latchrelease pawl and a latch release pawl pushing member in effect when acartridge is entered normally;

FIG. 42B is a schematic view depicting the relationship between thelatch release pawl and the latch release pawl pushing member in effectwhen a cartridge is entered erroneously;

FIG. 43 is a partial sectional plan view of a door locking mechanism;

FIGS. 44A through 44C are schematic views illustrating how a cartridgeis entered normally;

FIGS. 45A through 45C are schematic views portraying how a cartridge isentered erroneously;

FIG. 46 is a schematic plan view showing an alternative faulty cartridgeentry detecting mechanism;

FIG. 47 is a view of an operation panel for cartridge switchingoperations;

FIG. 48 is a block diagram of a typical control system for controllingthe magnetic tape library apparatus embodying the invention;

FIG. 49 is a block diagram of an accessor controller unit;

FIG. 50 is a schematic diagram of a nonvolatile memory;

FIG. 51 is a view of a typical cartridge switching table;

FIG. 52 is a flowchart of steps for switching cartridges according tothe invention;

FIG. 53 is a flowchart of steps carried out by a host computer inswitching cartridges;

FIG. 54 is a flowchart of steps carried out by the accessor controllerin switching cartridges;

FIG. 55 is a flowchart of steps effected by the accessor controller whenpower is applied; and

FIG. 56 is a front view of a bar coder reader and a bar code readerswinging mechanism;

FIG. 57 is a plan view of the components shown in FIG. 56;

FIG. 58 is a left-hand side view of the components shown in FIG. 56;

FIGS. 59A through 59E are views depicting how the bar code reader isswung;

FIG. 60 is a flowchart of steps for controlling a motor that swings thebar code reader;

FIG. 61 is a flowchart of steps for controlling in an alternative mannerthe motor that swings the bar code reader;

FIG. 62 is a block diagram of an automatic baud rate setting circuit ofthe bar code reader; and

FIG. 63 is a flowchart of steps for automatically setting a baud ratefor the bar code reader.

DESCRIPTION OF THE PREFERRED EMBODIMENTS:

FIG. 1 is a front perspective view of a magnetic tape library apparatus2 practiced as one preferred embodiment of the invention, and FIG. 2 isa rear perspective view of the embodiment. A housing 4 of the magnetictape library apparatus 2 has at its front a cartridge entry opening 6, acartridge exit opening 8, and operation panels 7 and 9. The cartridgeentry opening 6 is capable of admitting up to, say, 10 magnetic tapecartridges at a time. The cartridge exit opening 8 stacks up to, say, 15cartridges at a time. At the back of the housing 4 are a door 10 andanother operation panel 11. The door 10 allows a large number ofcartridges to move into and out of a row of cells in a cell drum, to bedescribed later. The door 10 has a transparent window 10a that permitsobservation of the cell drum inside. FIG. 3 shows how a magnetic tapecartridge 30 is entered through the cartridge entry opening 6, and FIG.4 depicts how a magnetic tape cartridge 30 is entered directly into acell of the cell drum when the door 10 is left open.

In FIGS. 5 and 6, the cell drum 12 is attached fixedly to a rotatablydriven shaft 14, the drum having a plurality of cells 18 separated bypartitions 16. The cell drum 12 is driven by a motor 15 via a geartrain, not shown. Adjacent to the cell drum 12 are two magnetic tapedrive units 28 for writing and reading data to and from magnetic tapes.Between the cell drum 12 and the magnetic tape drive units 28 is anaccessor 20 that automatically switches magnetic tape cartridges 30therebetween; the cartridges 30 are loaded into the magnetic tape driveunits 28 for read and write operations. In FIG. 5, reference numeral 32indicates a cartridge entry/exit mechanism connected to the cartridgeentry opening 6 and cartridge exit opening 8 of FIG. 1. An accessorcontroller 33 controls the operation of the accessor 20, cell drum 12,and cartridge entry/exit mechanism 32. A director 34 controls the writeand read operations of data to and from magnetic tape cartridges in themagnetic tape drive unit 28.

The drive mechanism of the accessor 20 is constructed as shown in FIG.7. A driving pulley 38 and a driven pulley 40 are attached rotatably toan approximately C-shaped support member 36. A timing belt 42 isthreaded around the pulleys 38 and 40 in an endless manner. The C-shapedsupport member 36 is secured with a guide member 22 extendingperpendicularly. Another support member 24 is fixed to the timing belt42. One end of the support member 24 is engaged with the guide member22. A hand mechanism 26 with a grip hand 25 is mounted on the supportmember 24.

When a motor 44 is activated, the support member 24 fixed to the timingbelt 42 moves up and down, guided by the guide member 22. That in turnmoves vertically the hand mechanism 26 mounted on the support member 24.When a motor 46 is activated, the support member 24 swings horizontally,with the guide member 22 acting as the center of the swing motion. Thatis, the hand mechanism 26 also swings horizontally. Where the motors 44and 46 are activated selectively under appropriate control, the handmechanism 26 is led to gain access to a selected cell 18 in the celldrum 12 as well as to a selected magnetic tape drive unit 28.

The drive mechanism of the accessor 20 is appreciably simplified becauseit is composed only of the above-described vertical direction drivemechanism and of the swing mechanism centering on the guide member 22.In practice, the cell drum 12, magnetic tape drive units 28 andcartridge entry/exit mechanism 32 are located around the accessor 20 insuch a manner that largely the swing motion of the accessor 20 alone(along with a limited vertical movement) will effect delivery ofmagnetic tape cartridges among these components.

Referring to FIG. 8A, a tape reel 52 is housed rotatably inside amagnetic tape cartridge 30. The base of a magnetic tape 54 is secured tothe tape reel 52, and the intermediate tape portion starting from thebase is wound around the reel 52. The tip of the magnetic tape 54 isequipped fixedly with a leader block 56. The leader block 56 has anengagement groove 56a with which a sled pin of the magnetic tape driveunit 28 is to be engaged. A cutout 58 is formed in one corner of themagnetic tape cartridge 30. The magnetic tape cartridge 30 has on itstop a depression 51 on which a label is pasted. The bottom of thecartridge 30 has a pair of parallel ridges 53 that engages with thedepression 51, as depicted in FIG. 8B.

FIG. 9 is a front view of a cartridge entry unit 68 for enteringmagnetic tape cartridges into the magnetic tape library apparatus 2. Thecartridge entry unit 68 comprises a stacker 70 for stacking a pluralityof magnetic tape cartridges, a stage mechanism 72, a hook mechanism 74,a feeder mechanism 76, a gate sensor mechanism 78 and a shuttermechanism 80. The stacker 70 is a box-like part that admits a pluralityof magnetic tape cartridges 30 entered by an operator. The stacker 70 isconnected to the cartridge entry opening 6 shown in FIG. 1. Cartridges30 entered into the stacker 70 are stacked thereby onto a stage 82 ofthe stage mechanism 72. The gate sensor mechanism 78 checks to see ifthe stacked cartridges 30 are correctly entered.

As will be explained later in more detail, the stage mechanism 72 movesthe stage 82 up and down. The hook mechanism 74 separates thelowest-positioned cartridge alone from the remaining multiple cartridges30 stacked on the stage 82. The feeder mechanism 76 transports to theaccessor 20 the single cartridge 30 separated from the cartridge stackby the hook mechanism 74. The shutter mechanism 80 stops temporarily thecartridge fed by the feeder mechanism 76 so as to keep the cartridgefrom falling off the feeder mechanism 76.

FIG. 10 is a view showing the path through which a cartridge istransported by the magnetic tape cartridge entry unit that is part ofthe embodiment. The cartridge 30 is entered into the stacker 70 in thearrowed direction M with its cutout 58 facing the front right side.Inside the stacker 70, the lowest-positioned cartridge alone isseparated from those thereabove by the stage mechanism 72 and hookmechanism 74, to be described later in more detail. The separatedcartridge 30 is transported by the feeder mechanism 76 in the arroweddirection N with the direction of the cartridge at its entry keptunchanged. After getting stopped temporarily by the shutter mechanism80, the cartridge 30 is delivered to the accessor 20.

The gate sensor mechanism 78 for detecting a faulty entry of cartridgeswill now be described with reference to FIGS. 9, 11A and 11B. As shownin FIG. 9, a gate actuator 60 is fixed to a shaft 61 which is adjacentto one side of the stacker 70 and which, supported rotatably thereby,extends in the vertical direction. The gate actuator 60 extends alongthe entire length of the stacker 70 and is biased rotatably with aspring 62 in the arrowed direction R. The top of the gate actuator 60 isequipped with a flag piece 64. A transmission type photo sensor 65having a light-emitting diode 66 and a photo-diode 67 is provided in theposition into which the flag piece 64 may be inserted.

With no cartridge entered, the gate actuator 60 remains pushed by thespring 62 to rotate sufficiently in the arrowed direction R. In thisstate, the photo-diode 67 receives light from the light-emitting diode66 and turns on the photo sensor 65. When the cartridge 30 is entered,the gate actuator 60 is pushed by the cartridge to rotate clockwise.

If the cartridge 30 is not fully entered into the stacker 70 or isentered in an incorrect direction, the gate actuator 60 is pushed by theerroneously entered cartridge to rotate clockwise. This causes the flagpiece 64 to be inserted into the photo sensor 65 before the gateactuator 60 stops. In this state, the flag piece 64 shields light fromthe light-emitting diode 66 and thereby turns off the photo sensor 65.The faulty entry of the cartridge 30 is detected in the manner above.

When the cartridge 30 is entered fully into the stacker 70 in thecorrect direction, the cutout 58 on the cartridge 30 allows the gateactuator 60, which was rotated clockwise earlier by the push from thecartridge 30, to rotate counterclockwise, i.e., in the arrowed directionR pushed by the spring 62. The action pulls the flag piece 64 out of thephoto sensor 65 and thereby turns it on. This allows the normal entry ofthe cartridge 30 to be detected. At this point, the cartridge 30 islocked to prevent its inadvertent fall from the stacker 70 because thegate actuator 60 interferes with the cutout 58 of the cartridge 30.

How the gate sensor mechanism 78 is illustratively practiced will now bedescribed with reference to FIGS. 9 and 12A through 12C. The photosensor 65 is attached to a plate member 63 fixed to the top plateconstituting part of the stacker 70. The photo sensor as practiced herechecks only for a faulty entry of the cartridge 30; whether or not thecartridge 30 is placed on the stage 82 will be detected by a separatelyprovided stage sensor. When the cartridge 30 is stacked on the stage 82,the stage sensor made illustratively of a photo sensor is turned off.This signals the detection of a cartridge entry into the stacker 70.That is, the combination of the gate sensor mechanism 78 with the stagesensor makes it possible to ascertain whether or not a plurality ofcartridges have been entered normally into the stacker 70.

If the cartridge 30 is inserted into the stacker 70 in an incorrectdirection, as depicted in FIG. 12A, the gate actuator 60 is pushed bythe side wall of the cartridge 30 and fails to return to its homeposition. This leaves the flag piece 64 inserted in the photo sensor 65.As a result, the photo-diode 67 does not receive light from thelight-emitting diode 66 and thus turns off the photo sensor 65. Thissignals the detection of a faulty entry of the cartridge 30. FIG. 12Bshows a case in which the cartridge 30 is entered insufficiently intothe stacker 70 in the correct direction; the cartridge 30 has notreached the far side of the stacker 70. In this case, as with the caseof FIG. 12A in which the cartridge was entered in the reverse direction,the gate actuator 60 fails to return to its home position, leaving theflag piece 64 inserted in the photo sensor 65. Consequently, thephoto-diode 67 does not receive light from the light-emitting diode 66and turns off the photo sensor 65. This also signals the detection of afaulty cartridge entry.

FIG. 12C portrays the cartridge 30 as it is entered correctly into thestacker 70. In this state, the cutout 58 formed in the front rightcorner of the cartridge 30 allows the gate actuator 60, which wasrotated clockwise earlier by the push from the cartridge 30, to returnto its home position biased by the spring 62. The tip of the gateactuator 60 comes into contact with the cutout 58. The contact pulls theflag piece 64 out of the photo sensor 65. Extracting the flag piece 64allows the photo-diode 67 to receive light from the light-emitting diode66, thereby turning on the photo sensor 65. This signals the detectionof a correct entry of the cartridge 30 into the stacker 70. In thisstate, the tip of the gate actuator 60 is kept in contact with thecutout 58 of the cartridge 30 by the spring 62. Thus the cartridge 30 islocked as entered into the stacker 70. As described, the gate sensormechanism 78 of the embodiment is capable of detecting a faulty entry ofany one of a plurality of (e.g., 10) cartridges 30 entered at a time.

The constitution and operation of the hook mechanism 74 will now bedescribed with reference to FIGS. 13, 14A and 14B. The hook mechanism 74comprises a front hook 100 and a rear hook 102 whose bottoms areattached pivotably to brackets 96 and 98 fixed to an apparatus frame 84.The tips 100a and 102a of the front and rear hooks 100 and 102 are bentas illustrated. As show in FIG. 13, the hook mechanism 74 has a sidehook 105 to which a bracket 109 is fixed. The bracket 109 can come intocontact with a roller 107 attached to the rear hook 102. FIG. 13 showsthe state in which the hooks 100, 102 and 105 are all closed. The sidehook 105 is closed by the push from the rear hook 102.

As depicted clearly in FIGS. 14A and 14B, one end of an L-shaped arm 106is attached pivotably to the front hook 100; one end of an L-shaped arm108 is also attached pivotably to the rear hook 102. The other ends ofthe arms 106 and 108 are attached pivotably to eccentrically positionedshafts on a rotor 104. The rotor 104 is fixed to an output shaft 103a ofa hook motor 103, as depicted in FIG. 13.

FIG. 14A portrays the front hook 100 and rear hook 102 rotated in adirection in which the tips of the hooks move away from each other. Withthe roller 107 leaving the bracket 109, the side hook 105 also moves toan opened position. In this state, the hook motor 103 is activated torotate the rotor 104 in the arrowed direction F of FIG. 14A. Therotation of the rotor 104 turns the front hook 100 and rear hook 102 viathe arms 106 and 108 so that the tips of the hooks move closer to eachother. As shown in FIG. 14B, the tips 100a and 102a of the front hook100 and rear hook 102 are inserted between the lowest-positionedcartridge 30 and the next-lowest cartridge 30. The stacked cartridgesabove the lowest-positioned cartridge 30 are raised therefrom by thehooks by about 2 mm. In this manner, the lowest cartridge 30 isseparated from the remaining cartridges.

The constitution and operation of the stage mechanism 72 will now bedescribed in detail together with the operation of the hook mechanism 74with reference to FIGS. 15A and 15B. A bracket 86 fixed to the apparatusframe 84 supports a shaft 90 rotatably. A gear 88, fixed to the shaft90, engages with a gear 87 coupled to a stage motor, not shown. A stagecam 92 is fixed eccentrically to the shaft 90. A cam follower 94 thatfollows the stage cam 92 is attached rotatably to the stage 82.

FIG. 15A shows the stage 82 at its highest position. The front hook 100,rear hook 102 and side hook 105 are all opened. These hooks are thuspositioned away from the cartridges 30 placed on the stage 82. In thisstate, the stage 82 is pushed to its highest position by the stage cam92. Activating the stage motor in this state causes the stage cam 92 torotate counterclockwise via the gears 87 and 88, whereby the stage 82starts coming down. The cartridges 30 placed on the stage 82 are alsolowered along with the stage.

With the stage 82 lowered to its lowest position, the hook motor 103 isactivated to rotate the rotor 104 counterclockwise, as depicted in FIG.14A. This in turn rotates the front hook 100 and rear hook 102 so thattheir tips 100a and 102a move closer to each other. As shown in FIG.15B, the tips 100a and 102a of the front hook 100 and rear hook 102 areinserted between the lowest-positioned cartridge and the second-lowestcartridge stacked on the stage 82. Then the second-lowest and highercartridges are lifted by about 2 mm, as described, whereby the lowestcartridge is separated from the remaining cartridges. The gap G of about2 mm is needed by the feeder mechanism 76 to transport the separatedcartridge 30, as will be described later. If a sufficient gap G is notobtained, the lowest-positioned cartridge 30, after separation from theother cartridges, will interfere with the cartridge immediately abovewhen transported by the feeder mechanism 76.

The lowest cartridge 30 thus separated is gripped, with its orientationunchanged, by the feeder mechanism 76. The feeder mechanism 76transports the cartridge 30 to the appropriate position for delivery tothe accessor 20. The constitution and operation of the feeder mechanism76 will now be described with reference to FIGS. 16A and 16B. L-shapedcatch arms 114 and 116 are attached with pins 115 and 117 pivotably tobrackets 110 and 112, respectively. One end of the catch arm 114 iscoupled rotatably with a pin 118 to one end of the catch arm 116. Aplurality of feed rollers 120 are attached rotatably to the top of thecatch arm 114; a plurality of feed rollers 122 are also attachedrotatably to the top of the catch arm 116. An endless belt 130 isthreaded around the feed rollers 122. The catch arm 116 is equipped witha feed motor 124. Activating the feed motor 124 rotates one of the feedrollers 122 via gears 126 and 128.

An actuator member 132 is coupled to the catch arm 116. The tip of theactuator member 132 has two engagement grooves 132a and 132b. The bottomof a support member 134 has an engagement groove 134a. The two ends of acoil spring 136 are engaged with the engagement grooves 132a and 134a. Aself-holding type feeder solenoid 138 is attached to the support member134. A coil spring 140 is disposed between a plunger 139 of the feedersolenoid 138 and the engagement groove 132b of the actuator member 132.

When the solenoid 138 is not magnetized, the actuator member 132 ispulled downward by the coil spring 136. This causes the two catch arms114 and 116 to rotate away from each other. As shown in FIG. 16A, theroller 120 and feed belt 130 are not in contact with the sides of thecartridge 30. In this state, momentarily magnetizing the self-holdingtype solenoid 138 causes the plunger 139 to spread the coil spring 140and to raise the actuator member 132 against the force of the coilspring 136. That in turn rotates the two catch arms 114 and 116 towardeach other. As depicted in FIG. 16B, the feed roller 120 and feed belt130 come in elastic contact with the sides of the cartridge 30. In thisstate, activating the feed motor 124 rotates the feed belt 130 totransport the cartridge 30 to the appropriate position for delivery tothe accessor 20.

While the cartridge 30 is being transported to the appropriate positionfor delivery to the accessor 20, an excessively driven feed motor 124can cause the cartridge to fall off the feeder mechanism 76. Such fallis prevented by the shutter mechanism 80 that positions the cartridge 30so as to ensure delivery to the accessor 20. The constitution andoperation of the shutter mechanism 80 will now be described withreference to FIGS. 17A and 17B. A shutter 144 is attached pivotably to ashaft 146 of a bracket 142. A bracket 148 is equipped with a solenoid150. The shutter 144 is coupled pivotably to the solenoid 150 with a pin152. FIG. 17A depicts the shutter 144 as it is lowered after thesolenoid 150 is demagnetized. FIG. 17B shows the shutter 144 rotatedcounterclockwise by a magnetized solenoid 150 to block the transportpath of the cartridge 30.

The solenoid 150 is magnetized at approximately the same time that thefeed motor 124 is activated. The magnetized solenoid 150 turns theshutter 144 counterclockwise to block the transport path of thecartridge 30. Halfway through the transport path of the feeder mechanism76 is a sensor, not shown, which detects passage of the cartridge 30. Apredetermined time (e.g., 0.5 sec.) after passage of the cartridge 30 isdetected by the sensor, the feed motor 124 is deactivated. During thattime, the cartridge 30 collides with the shutter 144, slips for a whileand stops there. Thereafter, the solenoid 150 is demagnetized, and theshutter 144 is rotated back to its lowered position that does not blockthe transport path of the cartridge 30, as shown in FIG. 17A.

Until the accessor 20 comes to fetch the cartridge 30, the feedermechanism 76 keeps the cartridge 30 gripped. The cartridge 30 is heldgripped as follows. First, the self-holding type solenoid 138 ismomentarily magnetized. This raises the plunger 139 and keeps it there.Then the feed roller 120 and endless belt 130 laterally grip thecartridge in elastic fashion. When the accessor 20 has gripped thecartridge 30, the self-holding type solenoid 138 is supplied with acurrent that flows in the direction opposite to that used when theplunger 139 is attracted. The flow of the current releases the plunger139 from its attracted position. With the cartridge 30 thus disengagedfrom the feeder mechanism 76, the accessor 20 grips the cartridge 30 andbrings it to the appropriate cell of the cell drum 12.

How an embodiment of the automatic magnetic tape cartridge exit unit ispracticed will now be described with reference to FIGS. 18 through 23.The automatic magnetic tape cartridge exit unit 160 is communicated tothe cartridge exit opening 8 shown in FIG. 1. FIG. 18 is a front view ofthe automatic cartridge exit unit 160 in its entirety. The automaticcartridge exit unit 160 comprises a cartridge transport mechanism 162and a tray assembly 164 disposed under the cartridge transport mechanism162. The cartridge transport mechanism 162 receives the magnetic tapecartridge 30 delivered by the accessor 20, transports the cartridge 30to an appropriate position and releases it there. The magnetic tapecartridge 30 is inserted into the cartridge transport mechanism 162through an insertion opening 166.

The tray assembly 164 includes a rear wall 168 and a pair of side walls170 and 172. A tray 176 on which to receive the magnetic tape cartridge30 is connected to a tray driving mechanism 205, to be described later,via a pair of longitudinal slits 174 formed on the rear wall 168. Themagnetic tape cartridge 30 is placed on a cartridge-carrying surface176a of the tray 176. The rear wall 168 has a pair of projected guides178 that extend longitudinally.

The constitution and operation of the cartridge transport mechanism 162will now be described with reference to FIGS. 19 and 20. A pair ofL-shaped catch arms 180 are attached pivotably to shafts 182 that aredisposed horizontally. One end of one catch arm 180 is coupled rotatablyto one end of the other catch arm 180 with a pin 184. The other ends ofthe two catch arms 180 are each equipped with a guide bracket 186 thatextends horizontally. The guide brackets 186 are in turn provided withfeed mechanisms 192 and 192' which feed the magnetic tape cartridge 30.The right-hand side feed mechanism 192 comprises a plurality of feedrollers 188 and an endless belt 190 threaded around these rollers 188.The left-hand side feed mechanism 192' includes only a plurality of feedrollers 188 attached rotatably to the guide bracket 186.

One catch arm 180 is coupled to an actuator member 194. The actuatormember 194 is connected to one end of a push spring 196 as well as toone end of a release spring 200, as illustrated. The other end of thepush spring 196 is coupled to a self-holding type solenoid 198 thatdrives the catch arms 180. The other end of the release spring 200 isfixed to a frame 201 of the cartridge transport mechanism 162.Magnetizing the solenoid 198 rotates the two catch arms 180 around thehorizontal shafts 182 toward each other. This causes the feed mechanisms192 and 192' mounted at the tips of the catch arms 182 to be pressedagainst the sides of the magnetic tape cartridge 30, as depicted in FIG.19.

When the solenoid 198 is demagnetized, the release spring 200 pulls upthe actuator member 194, rotating the catch arms 180 around thehorizontal shafts 182 away from each other. This causes the feedmechanisms 192 and 192' to release the magnetic tape cartridge 30.Adjacent to the actuator member 194 is a sensor 202 that detects themotion of the catch arms 180. An output signal from the sensor 202permits detection of the opened or closed state of the catch arms 180. Afeed motor 204 is provided to drive the feed mechanism 192.

With the magnetic tape cartridge 30 inserted in the insertion opening166, the solenoid 198 is demagnetized, and the two catch arms 180 arerotated away from each other, as illustrated in FIG. 20. When themagnetic tape cartridge 30 is inserted between the two feed mechanisms192 and 192' through the insertion opening 166, the solenoid 198 ismagnetized. This rotates the catch arms 180 toward each other, causingthe feed mechanisms 192 and 192' mounted at the tips of the arms 180 togrip the sides of the magnetic tape cartridge 30 and keep it in anapproximately horizontal state.

Then activating the feed motor 204 causes the feed mechanisms 192 and192' to transport the magnetic tape cartridge 30 to the right in FIG. 18until the exit position above the tray assembly 164 is reached. With theexit position attained, the feed mechanism 192 is deactivated and thesolenoid 198 is demagnetized. This allows the release spring 200 toforce the catch arms 180 into rotation away from each other, as depictedin FIG. 20. The magnetic tape cartridge 30 then falls downward and intothe tray assembly 164.

FIG. 21 is a longitudinal sectional view of the tray assembly 164. Asillustrated, a frame 212 is furnished integrally on the rear wall 168.The bottom and the top of the frame 212 have a driving pulley 206 and adriven pulley 208, respectively, both rotatably disposed. An endlessbelt 210 is threaded around the driving pulley 206 and driven pulley208. The tray 176 is fixed to the endless belt 210 with a bracket. Whenthe endless belt 210 is rotated by the driving mechanism 205, the tray176 moves up and down along the rear wall 168.

Referring now to FIGS. 22 and 23, the tray driving mechanism 205includes a motor 216 attached to a bracket 214 fixed to the frame 212. Agear 218, fixed to the output shaft of the motor 216, engages with agear 220 fixed to a shaft 222. A worm gear, not shown, is attachedfixedly to the shaft 222. The worm gear engages with a worm wheel fixedto a shaft 224. Activating the motor 216 to rotate the shaft 222 turnsthe driving pulley 206 attached to one end of the shaft 224, whereby theendless belt 210 is rotated.

As shown in FIG. 23, the tray 176 is fixed to the endless belt 210 usinga bracket 226. Driving the motor 216 moves the bracket 226 fixed to thetray 176 in a vertically sliding manner along a guide 228. The tray 176has on its top the cartridge-carrying surface 176a. The tray 176 isattached slidingly to the rear wall, with the front end of thetray-carrying surface 176a disposed higher than the rear end thereof.

The tray 176 is initially in its raised position so as to receive thecartridge 30 released by the cartridge transport mechanism 162. Theheight of the cartridges 30 stacked on the tray 176 is detected by asensor, not shown, so that the tray 176 is lowered gradually andcorrespondingly. Up to about 15 cartridges are to be stacked on the tray176. Because the tray 176 is attached slidingly to the rear wall withthe front end of its cartridge-carrying surface 176a elevated, thecartridges 30 placed on the tray 176 will not fall forward.

The hand mechanism 26 will now be described in more detail withreference to FIG. 24. On a base 230, a tray 232 is provided slidingly. Apinion 236 engages with a rack 238 attached to the side of the tray 222.Activating a motor 234 rotates the pinion 236 to move the tray 232slidingly along a guide rail 240 between a retracted position shown inFIG. 24 and an advanced position projecting in front of the base 230. Ahand unit 242 is provided to grip the magnetic tape Cartridge.Activating a motor 244 moves the hand unit 242 slidingly between anadvanced position and a retracted position. When the motor 244 isactivated, a pinion not shown coupled to the motor 244 engages with arack not shown attached to the base 230 to thereby cause the hand unit242 to move between its advanced and retracted positions.

The hand unit 242 has at its tip the grip hand 25. The grip hand 25 isclosed and opened between gripping and releasing positions to grip andrelease the magnetic tape cartridge. The closing and the opening of thegrip hand 25 are effected by a driving mechanism comprising a motor,gear train and coil spring, to be described later. A photo sensor 248for positional correction is used to position the hand mechanism 26 withrespect to the cell drum 12 and magnetic tape drive unit 28. At thefront end of the base 230 is a photo sensor 250 for detecting thepresence of a cartridge. The base 230 also has a bar code reader 252mounted thereto that reads a bar code attached to the side of eachmagnetic tape cartridge gripped by the grip hand 25.

A detailed constitution of the grip hand 25 and the operation of thedriving mechanism thereof will now be described with reference to FIG.25. The grip hand 25 comprises a first L-shaped finger 264 attachedrotatably about a shaft 268 and a second L-shaped finger 266 attachedrotatably about a shaft 270. The first and the second fingers 264 and266 have at one end thereof gripping portions 264a and 266a,respectively, and have rotatably furnished rollers 286 at the other endthereof. The first and the second fingers 264 and 266 are attached sothat their gripping portions 264a and 266a are oriented outward. Theother ends 264b and 266b of these fingers, equipped with a roller 286each, are positioned in such a way as to cross each other.

A shaft 254 is operatively coupled to a driving motor, not shown. Afirst gear 256 and a cylindrical block 258 are fixed to the shaft 254.The cylindrical block 258 is furnished with a coil spring 260 thatbiases the first gear 256 rotatably in the arrowed direction Cindicated. The first gear 256 engages with a second gear 262. One end ofa link 272 is attached pivotably with a pin 274 to the first finger 264;the other end of the link 272 is attached pivotably with a pin 276 tothe first gear 256. One end of a link 278 is attached pivotably with apin 280 to the second finger 266; the other end of the link 278 isattached pivotably with a pin 282 to the second gear 262.

In operation, deactivating the motor causes the biasing force of thecoil spring 260 to rotate the first gear 256 counterclockwise, i.e., inthe arrowed direction C. The rotation of the first gear 256 causes thesecond gear 252 to turn clockwise. As a result, the first finger 264turns counterclockwise around the shaft 268 and the second finger 266turns clockwise around the shaft 270, the two fingers coming intoposition for gripping the sides of a magnetic tape cartridge. In thegripping position, the grip hand 25 grips the sides of the cartridgeelastically by the biasing force of the coil spring 260.

Activating the motor turns the first gear 256 to turn clockwise againstthe biasing force of the coil spring 260. This causes the second gear262 to rotate counterclockwise. As a result, the first finger 264 turnsclockwise around the shaft 268 and the second finger 266 turnscounterclockwise around the shaft 270, the grip hand 25 coming into theillustrated position for releasing the cartridge. During transition fromgripping position to releasing position of the grip hand 25, the rollers285 at the ends of the first and the second fingers 264 and 266 push themagnetic tape cartridge into the magnetic tape drive unit 28 or into acell 18, as will be described later in more detail.

How a cartridge is inserted into the magnetic tape drive unit will nowbe described with reference to FIGS. 26A and 26B to 29A and 29B. Theaccessor 20 first extracts the magnetic tape cartridge 30 from a givencell of the cell drum 12 and, as shown in FIGS. 26A and 26B, transportsthe cartridge up to the front of the magnetic tape drive unit 28. Duringcartridge transportation, the grip hand 25 grips the rear sides of thecartridge 30 as indicated. The overhang distance G of the grippingportions over the cartridge 30 is preferably about 15 mm.

As depicted in FIGS. 27A and 27B, the hand unit 242 then advances withthe grip hand 25 gripping the cartridge 30, inserting the cartridge intothe entry opening of the magnetic tape drive unit 28. Withoutoperational correction, the first and the second fingers 264 and 266 ofthe grip hand 25 would collide with the entry opening of the magnetictape drive unit 28 and would be unable to insert the cartridge 30 allthe way into the unit 28.

Instead, the cartridge pushing motor is activated to turn the gear 256of FIG. 25 clockwise against the biasing force of the coil spring 260.This causes the first finger 264 to rotate clockwise around the shaft268. The gear 262 engaged with the gear 256 is rotated therebycounterclockwise, and the second finger 266 turns counterclockwisearound the shaft 270. This causes the grip hand 25 to open and allowsthe rollers 286 at the tips of the first and the second fingers 264 and266 to move forward to contact the rear end of the cartridge 30, therebypushing the cartridge all the way into the magnetic tape drive unit 28,as illustrated in FIGS. 28A and 28B. During the pushing motion, thecartridge 30 is moved forward by the push applied at two points of itsrear end, each point being distanced substantially equally from thecenter line of the cartridge. This makes it possible to push cartridge30 into the magnetic tape drive unit 28 in a stable manner.

With the cartridge 30 fully inserted into the magnetic tape drive unit28, the grip hand 35 closes and the hand unit 242 moves back to itsretracted position, as indicated in FIGS. 29A and 29B. This completesthe operation of pushing the cartridge 30 into the magnetic tape driveunit 28.

If irregularities in assembling have disrupted the positionalrelationship among the accessor 20, cell drum 12 and magnetic tape driveunit 28, the push by the first and the second fingers 264 and 266 maynot be enough for pushing the cartridge 30 all the way in. In such acase, the hand unit 242 is allowed to advance further in thecartridge-pushing state of FIGS. 28A and 28B until the cartridge 30 isfully inserted. As is clear from the description above and from thefigures attached, the tray 232 is kept in its retracted position whilethe cartridge 30 is being pushed into the magnetic tape drive unit 28.

How the cartridge 30 is placed into a cell 18 of the cell drum 12 willnow be described with reference to FIGS. 30A and 30B to 33A and 33B. Asmentioned, the overhang distance G of the grip hand 25 in grippingcondition over the rear sides of the cartridge 30 is about 15 mm.Because the distance G is very short compared with the entire length ofthe cartridge 30, the cartridge 30 gripped by the grip hand 25 can fallforward as it enters the cell if left unsupported. Such fall isprevented by use of the tray 232. That is, when the cartridge 30 is tobe inserted into the cell 18, the tray 232 is moved forward so as tosupport the cartridge from below.

The hand mechanism 26 of the accessor 20 is positioned in front of thetarget cell 18 into which to place the cartridge 30. Then as shown inFIGS. 30A and 30B, the tray 232 is moved forward to enter the cell 18all the way. After this, the hand unit 242 is allowed to advance to pushthe cartridge 30 into the cell 18. Without operational correction, thefirst and the second fingers 264 and 266 of the grip hand 25 wouldcollide with the entrance to the cell 18 and would be unable to insertthe cartridge 30 all the way into the cell 18.

Instead, as depicted in FIGS. 31A and 31B, the driving mechanism of FIG.25 drives the grip hand 25 to move forward the rollers 286 attached tothe first and the second fingers 264 and 266. The rollers 286 push therear end of the cartridge 30 to insert the cartridge all the way intothe cell 18. With the cartridge 30 fully inserted in the cell 18, a pairof ridges 19 provided on the cell 18 engage with grooves 31 of thecartridge 30. The engagement keeps the cartridge 30 from gettingdislodged from the cell 18 by vibration or other disturbances.

After insertion of the cartridge into the cell 18 is completed, the tray232 is brought back to its retracted position, as illustrated in FIGS.32A and 32B. With the tray 232 retracted, the grip hand 25 closes andthe hand unit 242 returns to its retracted position, as shown in FIGS.33A and 33B. This completes the operation of inserting the cartridge 30into the target cell 18.

If irregularities in assembling have disrupted the positionalrelationship among the accessor 20, cell drum 12 and magnetic tape driveunit 28, the push by the first and the second fingers 264 and 266 inFIGS. 31A and 31B may not be enough for pushing the cartridge 30 all theway into the cell 18. In such a case, the hand unit 242 is allowed toadvance further in the cartridge-pushing state of FIGS. 31A and 31Buntil the cartridge 30 is fully inserted.

How the cartridge 30 is extracted from the cell 18 will now be describedwith reference to FIGS. 34A and 34B. With the cartridge 30 accommodatedin the cell 18, the grooves 31 on both sides of the cartridge 30 engagewith the ridges 19 of the cell 18. The engagement prevents the cartridge30 from getting dislodged from the cell 18.

The cartridge 30 is extracted from the cell 18 as follows. First thetray 232 is inserted into the cell 18, as depicted in FIG. 34A. Onceinside the cell 18, the tray 232 is raised through an opening 18a of thecell 18, as shown in FIG. 34B, to receive on its top the cartridge 30from above. Then the hand unit 242 advances to have the grip hand 25grip the sides of the cartridge 30. With its grip hand 25 gripping thecartridge 30, the hand unit 242 will return to its retracted positionsliding on the tray 232. Thereafter, the tray 232 is allowed to returnto its retracted position.

As described, extracting the cartridge 30 from the cell 18 involvesfirst having the tray 232 receive the cartridge 30 and then getting thegrip hand 25 to grip the cartridge 30. This procedure prevents thecartridge 30 from getting inadvertently raised from the tray 232 whilethe hand unit 242 is placing the cartridge 30 onto the base 230. Thusthe cartridge 30 is placed in normal attitude on the base 230.

FIG. 35 is a schematic perspective view of a cell drum driving mechanism290. In FIG. 35, a gear 292 is fixed to the rotary shaft 14. A gear 294engaging with the gear 292 is fixed to the output shaft 296 of the motor15. The gear ratio of the gear 292 to the gear 294 is illustrativelyabout 150 to 1. The gear ratio allows the output torque of the motor 15to be transmitted to the cell drum 12 in magnified fashion. A tachometer298, coupled directly to the output shaft 296 of the motor 15, outputssignals reflecting the revolutions and the rotating direction of theoutput shaft 296. The tachometer 298 is a two-phase type comprising twodiscs 300 having 500 slits each and a photo sensor, not shown. An outputsignal from the tachometer 298 enters the controller 33. In turn, thecontroller 33 drives the motor 15 by the amount representing exactly theentire rotation angle desired for the cell drum 12 to revolve. Thatentire rotation angle is the angle to be traveled for the target cellcolumn of the cell drum 12 to reach its destination.

FIG. 36 is a view outlining how the revolutions and the motor current ofthe motor 15 typically vary over time. In the acceleration regionindicated in FIG. 36, an acceleration current is supplied to the motor15 until both the cell drum 12 and the motor 15, starting from theirstopped state, reach predetermined speeds. The acceleration current isdetermined with the inertia and friction factor of the rotating partstaken into account. In the steady or constant speed region indicated, aholding current is fed to the motor 15 so that the cell drum 12 and themotor 15 will rotate at predetermined constant speeds. The holdingcurrent is determined as per the friction factor involved. In thedeceleration region indicated, a deceleration current Id, which isdetermined as per the inertial and friction factor involved, is suppliedto the motor 15 for a necessary time t_(s). With the motor 15 stopped, apositioning current is supplied to the motor 15 so that the cell drum 12will continually stay at the target position. The positioning current isdetermined as per the displacement of the cell drum 12 relative to thetarget position. The steady speed region is not mandatory. If the steadyspeed region is omitted, the supply of the acceleration current to themotor 15 is followed immediately by that of the deceleration current,and the holding current is not supplied. The motor 15 is subject toswitching control by pulse width modulation. That is, the motor 15 isfed with controlled pulse currents. The motor current shown in FIG. 36represents not the current actually flowing through the motor 15 but thecurrent indications corresponding to the driving torque of the motor 15.

A locking mechanism 301 in FIG. 35 is activated when the door 10 fordirectly entering and ejecting cartridges is opened. Activating thelocking mechanism 301 locks the cell drum 12 where it is.

Below is a description of how to enter and eject all at once a largenumber of cartridges to and from a given cell column of the cell drum 12through the door 10 for direct cartridge entry and exit. A faultycartridge entry detecting mechanism 308 of FIG. 40 is provided to keepthe cartridges from getting entered erroneously into the cell column.

Each magnetic tape cartridge 30 has in one corner thereof a cutout 58 asshown in FIGS. 8A and 8B. The partition 16 defining each cell 18 has acutout detecting portion 16a that corresponds to the cutout of thecartridge 30 in physically complementing fashion. When the cartridge 30is entered with its cutout 58 first into the cell 18, the cutout 58 fitssnugly into the cutout detecting portion 16a. This is the normal stateof cartridge entry. Here, this side of the cartridge 30 which faces theoutside is substantially flush with the edge 16b of the partition 16defining the cell 18; the cartridge 30 will not protrude from the edge16b.

Should the cartridge 30 be entered with its cutout 58 facing the outsideinto the cell 18, as shown in FIG. 37B, a corner of the cartridge 30hits the cutout detecting portion 16a which keeps the cartridge 30 frombeing inserted all the way. In that case, the cartridge 30 protrudes bya distance n from the edge 16b of the partition 16 of the cell 18. Itfollows that detecting the distance n between the protruding edge of thecartridge 30 and the partition edge 16b signals the detection of afaulty cartridge entry. This is the principle on which the faultycartridge entry detecting mechanism operates. How the mechanismillustratively works will now be described with reference to FIGS. 38through 45C.

In FIG. 40, a driving shaft 310, mounted rotatably, is biasedcounterclockwise by a torsion coil spring 312. The driving shaft 310 isthus pushed to a predetermined angular position defined by a stopper,not shown, and held therein. A rocking arm 314 is fixed to the drivingshaft 310. The tip of the rocking arm 314 is equipped with a latch pawl316 in rotatable fashion. The latch pawl is pushed by a torsion coilspring 318 to a predetermined angular position and held therein. A gear304 is attached rotatably via a bearing 322 to a shaft 320 fixed to anapparatus frame 302. A roller 306 is attached rotatably to the corner ofthe gear 304 that contacts the door 10, as illustrated in FIGS. 38 and39. A gear 324 engaging with the gear 304 is attached rotatably to thedriving shaft 310. A torsion coil spring 328 pushes the gear 324 to apredetermined angular position defined by a stopper, not shown, andkeeps it therein. The torsion coil spring 328 transmits the torque ofthe gear 324 to the driving shaft 310.

As clearly shown in FIG. 41, a lock pin 326 is fixed to the gear 324,the pin 326 coupling the rocking arm 314 to the gear 324 by engagingwith the latch pawl 316 of the rocking arm 314. An actuator 330,attached rotatably to the driving shaft 310, is pushed by a torsion coilspring 332 to a predetermined angular position defined by a stopper, notshown, and held therein. The torsion coil spring 332 transmits thetorque of the driving shaft 310 to the actuator 330 to rotate thelatter. A detecting piece 334 is furnished along the entire length ofthe tip of the actuator 330. The detecting piece 334 extends along thewhole length of the cell columns in the cell drum 12. A faulty entry ofat least a single cartridge is detected upon contact between thecartridge and the detecting piece. A latch release pawl 338 is attachedrotatably to the apparatus frame 302, the pawl 338 rotating around ahorizontal axis. A pushing member 336 is fixed to the actuator 330. Whenthe actuator 330 is rotated beyond a predetermined angle, the pushingmember 336 pushes the latch release pawl 338 downward, as portrayed inFIG. 42A.

In FIG. 43, a lock pawl 307 is attached pivotably with a shaft 305 to abracket 303 fixed to the apparatus frame 302. A coil spring 309 biasesthe lock pawl 307 clockwise. A roller 313 is attached rotatably to thetip of a lock member 311 fixed to the door 10. Closing the door 10engages the roller 313 with the lock pawl 307; the lock is effectedautomatically when the door 10 is fully closed. Since the lock pawl 307is held biased clockwise by the coil spring 309, the door 10 is lockedwith the roller 313 engaged with the lock pawl 307 the moment the door10 is closed.

To unlock the door 10 requires magnetizing momentarily a solenoid 315attached to the bracket 303. When magnetized momentarily, the solenoid315 causes the lock pawl 307 to turn counterclockwise and release theroller 313, thereby unlocking the door 10. A plurality of elasticcushions 317 are bonded to the door 10, as shown in FIG. 41. When thedoor 10 is closed, the cushions 317 are deformed elastically uponcontact with the apparatus frame 302. When the door 10 is unlocked, therestoring force of the elastic cushions 317 allows the door 10 to openautomatically.

In operation, the actuator 330 is in its home position in FIG. 44A, anda flag 330a fixed to the actuator 330 is inserted in a home positionsensor 340 made of a transmission type photo sensor. A door sensor 342,made of a transmission type photo sensor, detects the closure of thedoor 10. As depicted in FIG. 44A, the door 10 is first opened to havethe cartridge 30 entered in normal attitude into the cell 18. When thedoor 10 is closed, as illustrated in FIGS. 39 and 44B, the driving shaft310 turns clockwise via the gears 304 and 324, which causes the actuator330 attached to the driving shaft 310 to rotate clockwise as well. InFIG. 44B where the cartridge 30 is entered normally in the cell 18, thedetecting piece 334 at the tip of the actuator 330 comes into contactwith the cartridge 30. At this point, the pushing member 336 rotates tothe position of FIG. 42A where the latch release pawl 338 is pushedthereby downward. Here, the door 10 is yet to be closed completely.Pushing further the door 10 causes the gear 304 to rotate the gear 324.

With the gear 324 turned further, the latch pawl 316 coupling the gear324 to the rocking arm 314 hits the latch release pawl 338 that waspushed down by the pushing member 336. This causes the latch pawl 316 todisengage from the lock pin 326 and separates the gear 324 from therocking arm 314. Only the gear 324 is allowed to turn further clockwise,while the driving shaft 310 is rotated in reverse by the torsion coilspring 312 to reach its home position, as shown in FIG. 44C. The flag330a is inserted into the home position sensor 340 to turn it on. Whenthe door 10 is locked in its closed position, the door sensor 342 isturned on. When both the home position sensor 340 and the door sensor342 are turned on, the cartridge 30 is judged to be entered normally inthe cell 18.

Suppose that the cartridge 30 is entered in the reverse direction intothe cell 18, as shown in FIG. 45A. In that case, closing the door 10halfway causes the detecting piece 334 at the tip of the actuator 330 tocollide with the cartridge 30, as portrayed in FIG. 45B. Because theposition of the cartridge 30 in this state is shallower than in thenormally entered state, the pushing member 336 cannot rotatesufficiently to push down the latch release pawl 338, as depicted inFIG. 42B. Pushing in the door 10 further allows the torque of the gear304 to rotate the gear 324 more. Because the gear 324 is coupled to therocking arm 314 by the latch pawl 316, the driving shaft 310 rotates.However the actuator 330, having hit the cartridge 30, cannot rotatehere and the pushing member 336 is held stopped.

Because the latch release pawl 338 is not pushed down by the pushingmember 336, the latch pawl 316 of the rocking arm 314 stays engaged withthe lock pin 326. The gear 324 and driving shaft 310 rotate further inthe door pushing direction until the door is closed and automaticallylocked. The coil spring 332 coupling the actuator 330 elastically to thedriving shaft 310 acts as a buffer. That is, the actuator 330 remainsstationary as the driving shaft 310 rotates. As a result, the door 10 isfully closed but the actuator 330 does not return to its home position,as shown in FIG. 45C. Thus when the door sensor 342 is turned on and thehome position sensor 340 is turned off, the cartridge 30 is judged tohave been entered erroneously into the cell 18.

FIG. 46 is a schematic plan view showing an alternative faulty cartridgeentry detecting mechanism. With the preceding faulty cartridge entrydetecting mechanism 308, the gear 304 pushed by the door 10 rotates thegear 324. With the door 10 opened, the greater part of the gear 304protrudes out of the apparatus frame 302. The alternative faultycartridge entry detecting mechanism 308' dispenses with the gear 304 andhas the gear 324 rotated using a gear 346 fixed to the output shaft of amotor 344. The remaining components of the alternative mechanism 308'are the same as those of the preceding mechanism 308.

When the motor 344 is turned, the detecting piece 334 at the tip of theactuator 330 collides with the cartridge 30 entered in the cell 18 andsignals a faulty cartridge entry. In FIG. 46, reference character Aindicates the state of normal cartridge entry; B denotes an abnormalstate of cartridge entry; and H stands for the home position of theactuator 330. The motor 344 is activated illustratively when the doorsensor 342 detects the closure of the door 10. Because the motor 344rotates the actuator 330, the mechanism 308' can keep the actuator 330at a constant operating speed while simplifying the entire apparatusstructure.

The constitution of the operation panel 11 for cartridge switchingoperations will now be described with reference to FIG. 47. A DEE lamp350 is a light-emitting diode which, when glowing, indicates cartridgeswitching is in progress. An OPEN lamp 352 is a light-emitting diodeindicating that the door 10 is ready to be opened. A STATUS display 354is a light-emitting diode arrangement showing a column number of thecell drum 12.

A cartridge switching request switch (DEE REQ) 356 is used to startcartridge switching, and a cartridge switching end switch (DEE END) 358when pushed ends cartridge switching. A cartridge holding cell selectingswitch (SELECT) 360 is used to select a cartridge holding cell 18. Adoor opening switch (DOOR OPEN) 362 when pushed opens the door 10. Anerror reset switch (RESET) 364 is used to reset an error that may occurduring cartridge switching.

FIG. 48 is a block diagram of a typical control system for controllingthe magnetic tape library apparatus 2 embodying the invention. In FIG.48, a magnetic tape controller (i.e., director) 34 controls the magnetictape drive unit 28 in writing and reading data to and from magnetictapes. An accessor controller unit 33 comprises an accessor controller366 and an accessor servo controller 368. The accessor controller 366communicates with a host computer 370 and receives and processes signalsfrom the various sensors and switches configured. The accessor servocontroller 368 controls the operation of the accessor 20, the activationand deactivation of the cell motor 15, the opening and closure of thedoor 10, and the operation of the cartridge entry/exit mechanism 32.

As shown in FIG. 49, the accessor controller 366 comprises an MPU 372connected via a bus 374 to a communication LSI 376, a RAM 378, acommunication memory 380, an I/O port 382, a nonvolatile memory 384 anda power supply supervisor 386. The nonvolatile memory 284 retains dataabout that cell column of the cell drum 12 in which cartridges areswitched manually as the door 10 is opened. When the door sensor 342detects the opening of the door 10, the data about the cell column inthe cartridge switching position of the cell drum 12 are stored in thenonvolatile memory 384. The power supply supervisor 386 detects theactivation and deactivation of the power supply to the apparatus.

As depicted in FIG. 50, the nonvolatile memory 384 includes a staticrandom access memory array (S-RAM array) 388 and an electricallyerasable and programmable read only array (EEPROM array) 390. The S-RAMarray 388 is connected with an address control circuit 392 that receivesaddress signals, a control circuit 394 that receives various controlsignals, and a data control circuit 396 to and from which data signalsare input and output.

In response to a store signal entered in the control circuit 394, thenonvolatile memory 384 of the above constitution can storeinstantaneously to the EEPROM array 390 (in arrowed direction S) thedata written in the S-RAM array 388, the data being based on the addresssignal, data signal and write signal supplied. Conversely, in responseto a recall signal entered in the control circuit 394, the nonvolatilememory 384 can retrieve instantaneously to the S-RAM array 388 (inarrowed direction R) the data stored in the EEPROM array 390.

While the magnetic tape library apparatus 2 is operating normally, thedetection of a magnetic tape cartridge switching operation based on thesignal from the door sensor 342 prompts the data on the cell column inwhich cartridges were switched to be stored into the S-RAM array 388.When the power supply supervisor 386 detects the deactivation of thepower supply to the apparatus, the data stored in the S-RAM array 388are saved into the EEPROM array 390 in response to the store signal.Later, when the power supply is again activated, the data on the cellcolumn in which the cartridges were switched are read from the EEPROMarray 390 and sent to the host computer 370 in accordance with therecall signal.

A cartridge switching table such as one in FIG. 51 is provided in thenonvolatile memory 384. When cartridges are switched, this table is usedto accommodate the data about the cell column in which the cartridgesare switched. For example, hexadecimal data "FF" are stored to representeach cell column in which the cartridges were switched. The other cellcolumns in which no cartridges were switched are represented by data"00" stored. With this scheme illustratively in effect, the table ofFIG. 51 indicates that cartridges were switched in the second and thethird cell columns.

How cartridges are switched in a given cell column of the cell drum 12will now be described with reference to FIGS. 52 through 55. Referringto FIG. 52, a large number of cartridges are entered or ejected manuallyall at once as follows. In step S1, the operator pushes the DEE REQswitch 356 on the operation panel 11 for cartridge switching. Pushingthe DEE REQ switch 356 transmits an interrupt request to the MPU 372 ofthe accessor controller 366. Upon completion of the interruption, theDEE lamp 350 glows in step S2. Viewing the STATUS display 354, theoperator verifies which cell column currently is facing the door 10. Ifthe indicated cell column is not the target cell column, the operatorpushes the SELECT switch 360 in step S3. The cell columns of the celldrum 12 rotate by one column every time the SELECT switch 360 is pushed.The operator pushes the SELECT switch 360 as many times as necessary. Instep S4, the operator checks to see if the target cell column now facesthe door 10. The check of step S4 is accomplished by viewing the STATUSdisplay 354 and by visually observing through the window 10a of the door10.

With the target cell column positioned behind the door 10, the OPEN lamp352 glows. In step S5, the operator pushes the DOOR OPEN switch 362.This magnetizes the solenoid 315 to unlock the door 10, allowing thedoor to open. When the door sensor 342 detects the opening of the door10, the detection signal from the door sensor 342 is input to theaccessor controller 366. In turn, the accessor servo controller 368causes the lock mechanism 301 of FIG. 35 to lock mechanically the celldrum 12 in rotation. That is, opening the door 10 results in locking thecell drum 12 mechanically.

With the door 10 opened, the operator enters or ejects necessarycartridges into or from the target cell column in step S6. With allcartridges entered or ejected, the operator closes the door 10 in stepS7. Closing the door 10 activates the door sensor 342. In step S8, acheck is made to see if the actuator 330 has returned to its homeposition. That is, step S8 checks to see if the home position sensor 340is turned on.

When the actuator 330 is found in step S8 to have returned to its homeposition, with all cartridges normally entered in the cells, a decisionis made in step S9 as to whether or not to switch cartridges in anothercell column. If cartridges need to be switched in another cell column,step S3 is reached again. The operator then pushes the SELECT switch 360as many times as needed, and steps S4 through S8 are repeated. If it isdecided that no cartridges need to be switched in any other cell columnin step S9, step S10 is reached in which the operator pushes the DEE ENDswitch 358 to terminate the cartridge switching operation. If a faultycartridge entry is detected in step S8, with the home position sensor340 held off, step S11 is reached. In step S11, an error indication onthe operation panel warns the operator of the cartridge entry failure. Abuzzer or the like may be activated simultaneously to reinforce thewarning to the operator. Having verified the error indication, theoperator reopens the door 10 to rearrange the cartridges in the cells.

How the host computer performs its processing will now be described withreference to FIG. 53. In step S21, the host computer 370 checks to seeif a cartridge switching end notice has been received from the accessorcontroller 366. If the end notice is found to be received, step S22 isreached. In step S22, the host computer 370 receives from the magnetictape library apparatus 2 the data on the cell column in which cartridgeswere switched. More specifically, when the operator pushes the DEE ENDswitch 358, the signal from the switch 358 enters the accessorcontroller 366 via the I/O port 382, and the cartridge switching endnotice is sent to the host computer 370 via the communication LSI 376.In this manner, the host computer 370 receives the data on the cellcolumn in which the cartridges were switched.

On receiving the cell column data, the host computer 370 tells theaccessor 20 to read bar codes off the cartridges 30 in the cell columnin question. The command is sent to the accessor 20 via the accessorcontroller 366 and accessor servo controller 368. In step S23, theaccessor 20 gains access to each cell 18 to extract the cartridgetherefrom.

In step S24, a check is made to see if the cartridge 30 exists in thecell 18 accessed. The check of step S24 is accomplished by use of thecartridge sensor 250 of FIG. 24. If the cartridge 30 is found in thecell in step S24, step S25 is reached. In step S25, the hand 25 of theaccessor 20 grips the cartridge 30 and takes it out of the cell. The barcode reader 252 reads the bar code off the cartridge 30 extracted, andthe cartridge 30 is returned to its cell 18. The bar code data read bythe bar code reader 252 off the cartridge 30 are stored into thecartridge data table of the host computer 370 via the accessorcontroller 366. If no cartridge is found in the accessed cell in stepS24, step S26 is reached. In step S26, the absence of cartridge iswritten to the cartridge data table of the host computer 370. In stepS27, a check is made to see if the bar codes of all cartridges in thecolumn cell have been read. If the bar code reading is found to beincomplete, steps S23 through S26 are repeated. When the bar codereading is completed on all cells involved, control returns to thenormal processing.

How the accessor controller unit 33 works will now be described withreference to the flowchart of FIG. 54. In step S31, a check is made tosee if the operator has pushed the SELECT switch 360. Pushing the SELECTswitch 360 once turns the cell drum 12 by one cell column in step S32.Steps S31 and S32 are repeated as many times as needed until the targetcell column comes immediately behind the door 10.

With the target cell column positioned to the door 10, the OPEN lamp 352glows. In response, the operator pushes the DOOR OPEN switch 362. Whenthe DOOR OPEN switch 362 is judged to be pushed in step S33, thesolenoid 315 is magnetized to unlock the door 10. This allows the door10 to be opened in step S34. The opening of the door 10 is detected bythe door sensor 342. In step S35, cartridge switching data are set tothe cartridge switching table 385 of FIG. 51 in the nonvolatile memory384. Then the closure of the door 10 is awaited in step S36.

When the door 10 is judged to be closed in step S36 and when the DEE ENDswitch 358 is judged to be pushed in step S37, step S38 is reached. Instep S38, the host computer 370 is notified of the data about the cellcolumn in which the cartridges were switched. In step S39, the cartridgeswitching table 385 in the nonvolatile memory 384 is cleared.

Described below with reference to the flowchart of FIG. 55 is how theaccessor controller 366 works when the apparatus is turned on afterremoval of power. In step S41, the apparatus is turned on, with a recallsignal generated. The recall signal prompts the cartridge switching datato be read from the EEPROM array 390. In step S42, a check is made tosee if the applicable cell column data, i.e., the data about the cellcolumn in which the cartridges were switched, are set in the cartridgeswitching table 385. If the applicable cell column data are found to beset, step S43 is reached. In step S43, the host computer 370 is notifiedof the cell column in which the cartridges were switched. In step S44,the cartridge switching table 385 in the nonvolatile memory 384 iscleared.

Referring again to FIG. 24, the base 230 of the hand mechanism 26 isequipped with the bar code reader 252 for reading a bar code off eachcartridge 30. The constitution of the bar code reader 252 will now bedescribed with reference to FIGS. 56 through 58. The bar code reader 252is mounted fixedly on a U-shaped attaching member 414. A U-shapedsupport member 400 is fixed to the base 230 of the hand mechanism 26.The support member 400 is equipped with the attaching member 414 towhich the bar code reader 252 is attached pivotably with a shaft 402.One end of an arm 412 is fixed to the attaching member 414; the otherend of the arm 412 has an oblong hole 412a formed vertically therein.

One end of an eccentric shaft 408 is fixed eccentrically to an outputshaft 406 of a motor 404. One end of a member 410 is fixed eccentricallyto the other end of the eccentric shaft 408. The other end of the member410 is inserted in the oblong hole 412a of the arm 412. A flag 416 isfixed to the eccentric shaft 408. A bar code sensor 418 made of atransmission type photo sensor is furnished in position for detectingthe flag 416. The motor 404 is illustratively a stepping motor fixed tothe base 230 of the hand mechanism 26 via a bracket, not shown. A cord420 connects the bar code reader 252 to the accessor controller 366.

In operation, rotating the motor 404 clockwise in FIG. 58 causes themember 410 attached to the eccentric shaft 408 to move slidingly insidethe oblong hole 412a of the arm 412. In so moving, the member 410 pushesthe arm 412 to the right in FIG. 58. As a result, the bar code reader252 rotates clockwise about the output shaft 406 of the motor.404, andthe state of FIG. 59B is attained. When the eccentric shaft 408 isturned by 90 degrees from the state shown in FIG. 56 and FIG. 59A, themember 410 moves slidingly down to the approximate middle of the oblonghole 412a of the arm 412 while pushing the latter. At this time, amaximum clockwise rotation angle of the bar code reader 252 is attained.

Thereafter, turning the motor 404 further clockwise causes the bar codereader 252 to rotate counterclockwise about the output shaft 406 of themotor 404. A 180-degree revolution of the eccentric shaft 408 results inthe state of FIG. 59C. A further 270-degree clockwise revolution of themotor 404 causes the bar code reader 252 to reach the maximumcounterclockwise rotation angle shown in FIG. 59D. One complete turn ofthe eccentric shaft 408 allows the bar code reader 252 to return to itshome position shown in FIG. 59E. Each turn of the eccentric shaft 408 isascertained by the bar code sensor 418 detecting the flag 416.

As described, the bar code reader 252 swings about the output shaft 406of the motor 404 in the direction S shown in FIG. 58. With the bar codereader 252 held horizontally, a window 252a emits a laser beamhorizontally in the arrowed direction H to scan the bar code of thecartridge 30. When the bar code reader 252 is swung clockwise, the laserbeam is emitted downward in the arrowed direction D to scan thecartridge bar code; when the bar code reader 252 is swungcounterclockwise, the laser beam is emitted upward in the arroweddirection U to scan the cartridge bar code. Because the bar code reader252 of the invention is attached swingingly to the base 230 of the handmechanism 26, the reader 252 can read the bar code off the cartridge 30even if the cartridge 30 gripped by the grip hand 25 is slightly out ofalignment with normal attitude.

How the bar code reader 252 reads a bar code will now be described withreference to the flowchart of FIG. 60. When the grip hand 25 grips thecartridge 30 and retracts it to a predetermined position, a sensor, notshown, detects the completion of the cartridge retracting motion. Adetection signal from the sensor causes step S51 to be entered. In stepS51, the bar code reader 252 is driven in stationary condition (i.e,without swinging) to read the bar code off the cartridge 30. In stepS52, a check is made to see if the bar code has been read. If the barcode is read successfully, the bar code reading operation is terminated.

If the bar code was not read successfully, step S53 is reached. In stepS53, the bar code motor 404 is rotated to swing the bar code reader 252in the arrowed direction S. In step S54, an attempt is made to read thebar code off the cartridge 30 while the motor 404 is rotating. In stepS55, a check is made to see if the bar code has been read. The readoperation of step S54 is repeated until the bar code has beensuccessfully read. In step S56, the bar code sensor 418 attempts todetect the flag 416. In step S57, a check is made to see if the flag 416is detected. When the bar code sensor 418 detects the flag 416, step S58is reached. In step S58, a braking instruction is fed to the motor 404to stop it. As described, if the cartridge bar code is not read whilethe motor 404 is in stopped state, this bar code reading method allowsthe bar code reader 252 to read the bar code while the eccentric shaft408 completes a single turn.

Another control method by which the bar code reader 252 reads the barcode will now be described with reference to the flowchart of FIG. 61.Steps S61 through S65 of this method are the same as steps S51 throughS55 of the preceding method of FIG. 60. The difference is that underthis alternative control method, the motor 404 is stopped in step S66 bysupplying it with a braking instruction in synchronism with a signalindicating the successful completion of the bar code reading detected instep S65. In step S67, the number of motor steps is counted from thetime the braking instruction is given to the motor 404 until the motoris actually stopped. The bar code motor 404 is then turned in reverseexactly by the number of the motor steps counted. That is, step S67represents the corrective action for moving the bar code reader 252 backto the position where the bar code was read. In step S68, the bar codereader 252 is stopped in the optimum position. With the bar code reader252 optimally positioned, there is no need to activate the bar codemotor 404 next time a bar code is to be read off the cartridge 30.

Under the preceding bar code reading method of FIG. 60, the eccentricshaft 408 must always make one complete turn if the bar code reader 252in its stopped position cannot read the bar code. By contrast, under thealternative bar code reading method of FIG. 61, the eccentric shaft 408need not execute one complete revolution, with the bar code reader 252stopped in its swing motion at the position where the bar code was readoff the cartridge 30. The latter method improves the possibility of thebar code reader 252 being optimally positioned for further bar codereading. Thus the bar code reader 252 need not be rotated when readingthe next bar code.

The fact that the bar code reader 252 is attached to the hand mechanism26 offers the following advantages: Suppose that the door 10 (for directcartridge entry and exit) is opened to let a large number of cartridgesenter into a given cell column of the cell drum 12. In that case, theprior art magnetic tape library apparatus typically has the accessortake the cartridges one by one out of the cell column in question, getsthe cartridge entry unit equipped with the bar code reader to read thebar code off each cartridge, and brings each cartridge back to theappropriate cell. According to the invention, the hand mechanism havingthe bar code reader 252 gains access directly to the cells of the columnwherein the cartridges were switched, as in step S23 of FIG. 53. If thecell accessed contains a cartridge, the grip hand 25 draws the cartridge30 into a predetermined position of the hand mechanism 26, and the barcode reader 252 reads the bar code off the cartridge 30.

The bar code data read by the bar code reader 252 off the cartridge 30are written to the cartridge data table of the host computer 370, as instep S25 of FIG. 53. With its bar code read, the cartridge is broughtback to the cell from which it was extracted earlier by the grip hand25.

The baud rate and other settings for the bar code reader 252 areestablished by commands from the accessor controller 366. These settingsare written to the nonvolatile memory inside the bar code reader 252.The baud rate of the bar code reader 252 needs to coincide with that ofthe accessor controller 366 for communication therewith. Illustratively,the initial baud rate for the two units is set to 9,600. The bar codereader 252 communicates with the accessor controller 366 at the baudrate of 9,600. In case the baud rate preset in the nonvolatile memory ofthe bar code reader 252 is lost due to electrical noise or otherdisturbances, the prior art bar code reader is incapable of having theaccessor controller set the necessary baud rate for communicationtherebetween.

This problem is resolved by the automatic baud rate setting circuit ofthe bar code reader according to the invention. This baud rate settingcircuit will now be described with reference to FIGS. 62 and 63. Theaccessor controller 366 comprises an MPU 372, a baud rate varyingcircuit 422 and an interface 382. The bar code reader 252 comprises aninterface 424, a decoding control circuit 426 for decoding bar codes,and a laser emission/reception circuit 428. The bar code reader 252further includes a nonvolatile memory 432 for storing baud rates andother settings, a baud rate write control circuit 430, and a baud ratesetting circuit 434 for setting the baud rate for the interface 424 inaccordance with the baud rate in the nonvolatile memory 432.

Described below with reference to the flowchart of FIG. 63 is how toreestablish the desired baud rate that has been lost from thenonvolatile memory 432 of the bar code reader 252. In step S71, theaccessor controller 366 transmits a communication command at a baud rateof 9,600 to the bar code reader 252. In step S72, a check is made to seeif the bar code reader 252 has acknowledged the command. If the commandis acknowledged, the processing is judged to be normal and control ispassed on to the next process. If the command is not acknowledged instep S72, step S74 is reached. In step S74, communication commands aretransmitted at different baud rates such as 300, 600, etc. The baud rateis varied in step S74 until the command is acknowledged by the bar codereader 252 in step S75. For example, if the command is acknowledged at abaud rate of 4,800, a baud rate setting command at the baud rate of4,800 is issued to set the baud rate in the nonvolatile memory 432 to9,600.

More specifically, in the setup of FIG. 62, the accessor controller 366sends to the bar code reader 252 at the baud rate of 4,800 the commandtelling the latter to set its baud rate to 9,600. The command is inputto the write control circuit 430 via the interface 424. In turn, thewrite control circuit 430 writes the baud rate of 9,600 to thenonvolatile memory 432. With the baud rate of 9,600 written in thenonvolatile memory 432, the baud rate setting circuit 434 reads thatbaud rate and sets the baud rate of the interface 424 to 9,600accordingly. Now that the baud rate of the interface 424 is set for thedesired baud rate of 9,600, the bar code reader 252 can communicate withthe accessor controller 366 at that baud rate.

Although the description above contains many specificities, these shouldnot be construed as limiting the scope of the invention but as merelyproviding illustrations of some of the presently preferred embodimentsof this invention. For example, the invention applies not only to theabove-described magnetic tape library apparatus handling magnetic tapecartridges but also to other library apparatuses dealing with generalrecording medium cartridges including optical disc cartridges.

Thus the scope of the invention should be determined by the appendedclaims and their legal equivalents, rather than by the examples given.

What is claimed is:
 1. A library apparatus comprising:a housing; a cellunit having a plurality of cell columns each including a plurality ofcells, each cell for accommodating a recording medium cartridge having abar code attached thereto; a recording medium drive unit for writing andreading data to and from a recording medium cartridge; a cartridge entryunit for entering recording medium cartridges into said libraryapparatus; a cartridge exit unit for ejecting recording mediumcartridges from inside said library apparatus; an accessor fortransporting cartridges between said cell unit, said recording mediumdrive unit, said cartridge entry unit and said automatic cartridge exitunit, said accessor including a hand mechanism for gripping a cartridgein a substantially horizontal manner, said hand mechanism including abase attached swingingly about a vertical axis, and grip means forgripping the recording medium cartridge at opposite side surfacesthereof, said grip means being movably mounted on said base between anadvanced position and a retracted position and being swingable about avertical axis; a bar code reader attached to said hand mechanism forreading the bar code off each recording medium cartridge, said bar codereader reading the bar code off the recording medium cartridge at afirst horizontally rotated position after said grip means gripping thecartridge has moved to said retracted position; swing means for rotatingsaid bar code reader about a horizontal axis; and control means foractivating said swing means to controlledly rotate said bar code readerabout said horizontal axis; and for controlling said bar code reader toread the bar code off the recording medium again at a second anddifferent horizontally rotated position when a first try of reading thebar code has failed at said first horizontally rotated position.
 2. Alibrary apparatus according to claim 1, further comprising a door forallowing a large number of recording medium cartridges to enter all atonce into the cells of a given cell column of said cell unit, said doorbeing attached pivotably to said housing adjacent to said cell unit. 3.A library apparatus according to claim 1 wherein:said control meansautomatically activates said swing means to continue controlled rotationof said bar code reader about said horizontal axis to effect bar codereading at additional horizontally rotated positions when previousattempts at reading the bar code have failed.
 4. A library apparatuscomprising:a housing; a cell unit having a plurality of cell columnseach including a plurality of cells, each cell accommodating a recordingmedium cartridge having a bar code attached thereto; a recording mediumdrive unit for writing and reading data to and from a recording mediumcartridge; a cartridge entry unit for entering recording mediumcartridges into said library apparatus; an automatic cartridge exit unitfor automatically ejecting recording medium cartridges from inside saidlibrary apparatus; an accessor for transporting cartridges through saidcell unit, said recording medium drive unit, said cartridge entry unitand said automatic cartridge exit unit, said accessor including a handmechanism for gripping a cartridge in a substantially horizontal manner;a door for allowing a large number of recording medium cartridges toenter all at once into the cells of a given cell column of said cellunit, said door being attached pivotably to said housing adjacent tosaid cell unit; a base attached swingingly about a vertical axis; andgrip means for gripping the recording medium cartridge movably mountedon said base between an advanced position and a retracted position, saidgrip means being swung about a horizontal axis; and swing means forswinging said bar code reader about a horizontal axis; wherein said barcode reader reads the bar code off the recording medium cartridge aftersaid grip means gripping the cartridge has moved to said retractedposition; and said swing means comprisessupport means fixedly secured tosaid base for supporting said bar code reader swingingably; an armfixedly secured at one end to said bar code reader, said arm having atthe other end thereof an oblong hole formed vertically therein; adriving motor having an output shaft; an eccentric shaft fixedeccentrically to the output shaft of said driving motor; and a memberfixedly secured at one end to said eccentric shaft and having the otherend inserted in the oblong hole of said arm.
 5. A library apparatusaccording to claim 4, wherein said swing means further comprises sensormeans for detecting one complete turn of said eccentric shaft. 6.Library apparatus according to claim 5, wherein said bar code readerreads the bar code off each recording medium cartridge when said sensormeans detects one complete turn of said eccentric shaft rotated by saidswing means.
 7. A library apparatus according to claim 5, wherein saidbar code reader reads the bar code off each recording medium cartridgewhile being swung by said swing means, said motor is stopped in responseto a braking instruction generated upon completion of the bar codereading, and then said motor is rotated in reverse for a predeterminedtime.
 8. A library apparatus comprising:a housing; a cell unit having aplurality of cell columns each including a plurality of cells, each cellfor accommodating a recording medium cartridge having a bar codeattached thereto; a recording medium drive unit for writing and readingdata to and from a recording medium cartridge; a cartridge entry unitfor entering recording medium cartridges into said library apparatus; acartridge exit unit for ejecting recording medium cartridges from insidesaid library apparatus; an accessor for transporting cartridges betweensaid cell unit, said recording medium drive unit, said cartridge entryunit and said cartridge exit unit, said accessor including a handmechanism for gripping a cartridge in a substantially horizontal manner;a bar code reader attached to said hand mechanism for reading the barcode off each recording medium cartridge, said bar code reader beingrotatable to a second and different horizontally rotated position when afirst try of reading the bar code has failed at a first horizontallyrotated position; and accessor control means for controlling saidaccessor, said accessor control means including baud rate varying meansfor varying a baud rate to establish a data communication baud rate;said bar code reader comprising a nonvolatile memory for storing baudrates, write control means for writing to said nonvolatile memory adesired baud rate relevant to the data communication with said accessorcontrol means in accordance with commands therefrom, said baud ratevarying means transmitting different baud rates to said bar code readeruntil compatible data communication is established, said write controlmeans using said established baud rate to write said desired baud rateto said nonvolatile memory, and baud rate setting means for setting saidbar code reader at said desired baud rate written in said nonvolatilememory.
 9. A library apparatus according to claim 8, further comprisinga door for allowing a large number of recording medium cartridges toenter all at once into the cells of a given cell column of said cellunit, said door being attached pivotably to said housing adjacent tosaid cell unit.
 10. A library apparatus comprising:a housing; a cellunit having a plurality of cell columns each including a plurality ofcells, each cell for accommodating a recording medium cartridge having abar code attached thereto; a recording medium drive unit for writing andreading data to and from a recording medium cartridge; a cartridge entryunit for entering recording medium cartridges into said libraryapparatus; an automatic cartridge exit unit for automatically ejectingrecording medium cartridges from inside said library apparatus; anaccessor for transporting cartridges between said cell unit, saidrecording medium drive unit, said cartridge entry unit and saidautomatic cartridge exit unit, said accessor including a hand mechanismfor gripping a cartridge in a substantially horizontal manner, said handmechanism including a base attached swingingly about a vertical axis, apair of fingers each having a gripping end for gripping the recordingmedium cartridge at opposite side surfaces thereof, said fingers beingmovably mounted on said base between an advanced position and aretracted position and being swingable about a vertical axis, each ofsaid fingers having a pushing end for pushing the recording mediumcartridge into the cell when the recording medium cartridge is insertedinto the cell by said accessor, and a tray movably mounted on said basebetween an advanced position and a retracted position, said traysupporting the recording medium cartridge when the recording mediumcartridge is gripped by said fingers; a bar code reader attached to saidhand mechanism for reading the bar code off each recording mediumcartridge, said bar code reader reading the bar code off the recordingmedium cartridge after said grip means gripping the cartridge has movedto said retracted position; and swing means for rotating said bar codereader about a horizontal axis, said swing means rotating said bar codereader to a second and different horizontally rotated position when afirst try of reading the bar code has failed at a first horizontallyrotated position.
 11. A library apparatus comprising:a housing; a cellunit having a plurality of cell columns each including a plurality ofcells, each cell for accommodating a recording medium cartridge having abar code attached thereto; a recording medium drive unit for writing andreading data to and from a recording medium cartridge; a door forallowing a large number of recording medium cartridges to enter all atonce into the cells of a given cell column of said cell unit, said doorbeing attached pivotably to said housing adjacent to said cell unit; anaccessor for transporting cartridges between said cell unit and saidrecording medium drive unit, said accessor including a hand mechanismfor gripping a cartridge in a substantially horizontal manner, said handmechanism including a base attached swingingly about a vertical axis,and grip means for gripping the recording medium cartridge at oppositeside surfaces thereof, said grip means being movably mounted on saidbase between an advanced position and a retracted position and beingswingable about a vertical axis; a bar code reader attached to said handmechanism for reading the bar code off each recording medium cartridge,said bar code reader reading the bar code off the recording mediumcartridge at a first horizontally rotated position after said grip meansgripping the cartridge has move to said retracted position; swing meansfor swinging said bar code reader about a horizontal axis; and controlmeans for activating said swing means to controlledly rotate said barcode reader about said horizontal axis; and for controlling said barcode reader to read the bar code off the recording medium again at asecond and different horizontally rotated position when a first try ofreading the bar code has failed at said first horizontally rotatedposition.
 12. A library apparatus according to claim 11, wherein saidswing means further comprises sensor means for detecting an amount ofrotational movement of said swing means.
 13. A library apparatusaccording to claim 12, wherein said bar code reader reads the bar codeoff each recording medium cartridge when said sensor means detects apredetermined rotational amount of said swing means.
 14. A libraryapparatus comprising:a housing; a cell unit having a plurality of cellcolumns each including a plurality of cells, each cell for accommodatinga recording medium cartridge having a bar code attached thereto; arecording medium drive unit for writing and reading data to and from arecording medium cartridge; a door for allowing a large number ofrecording medium cartridges to enter all at once into the cells of agiven cell column of said cell unit, said door being attached pivotablyto said housing adjacent to said cell unit; an accessor for transportingcartridges between said cell unit and said recording medium drive unit,said accessor including a hand mechanism for gripping a cartridge in asubstantially horizontal manner, a bar code reader attached to said handmechanism for reading the bar code off each recording medium cartridgesaid bar code reader being rotatable to a second and differenthorizontally rotated position when a first try of reading the bar codehas failed at a horizontally rotated position, and accessor controlmeans for controlling said accessor, said accessor control meansincluding baud rate varying means varying a baud rate to establish acommunication baud rate; said bar code reader comprising a nonvolatilememory for storing baud rates, write control means for writing to saidnonvolatile memory a desired baud rate for communication with saidaccessor control means in accordance with commands therefrom, said baudrate varying means transmitting different baud rates to said bar codereader unit communication is established, said write control means usingsaid established communication baud rate to write said desired baud rateto said nonvolatile memory, and baud rate setting means for setting saidbar code reader at said desired baud rate written in said nonvolatilememory.
 15. A library apparatus according to claim 14, furthercomprising:swing means for swinging said bar code reader about ahorizontal axis.
 16. A library apparatus comprising:a housing; a cellunit having a plurality of cell columns each including a plurality ofcells, each cell accommodating a recording medium cartridge having a barcode attached thereto; a recording medium drive unit for writing andreading data to and from a recording medium cartridge; a cartridge entryunit for entering recording medium cartridges into said libraryapparatus; a cartridge exit unit for ejecting recording mediumcartridges from inside said library apparatus; an accessor fortransporting cartridges through said cell unit, said recording mediumdrive unit, said cartridge entry unit and said automatic cartridge exitunit, said accessor including a hand mechanism for gripping a cartridgein a substantially horizontal manner, said hand mechanism including abase attached swingingly about a vertical axis, and grip means forgripping the recording medium cartridge at opposite side surfacesthereof, said grip means being movably mounted on said base between anadvanced position and a retracted position and being swingable about avertical axis; a bar code reader attached to said hand mechanism forreading the bar code off each recording medium cartridge, said bar codereader reading the bar code off the recording medium cartridge at afirst horizontally rotated position after said grip means gripping thecartridge has moved to said retracted position; swing means for rotatingsaid bar code reader about a horizontal axis to a second and differenthorizontally rotated position when a first try of reading the bar codehas failed at a first horizontally rotated position; and control meansfor activating said swing means to controlledly rotate said bar codereader about said horizontal axis.